Under what condition will ACMP 3B turn on automatically in the air?

ACMP 3B is designed to activate automatically in the air under specific conditions to ensure hydraulic system reliability and redundancy. When ACMP 3A experiences a failure, it decreases the available hydraulic pressure in the system; therefore, ACMP 3B will turn on to maintain hydraulic pressure and support the essential functions that rely on this hydraulic system.

This automatic activation is part of the aircraft's safety features, ensuring that critical systems remain operational even when there's a failure in one of the hydraulic pumps. Ensuring adequate hydraulic power is crucial for various operations, including flight controls and landing gear operation. Understanding the interdependencies between these components is essential for pilot decision-making and system management during flight.

The other options do not trigger the automatic activation of ACMP 3B in the same way. For instance, PTU activation is a manual or system-initiated response to pressure imbalances and does not relate directly to ACMP 3A's operational status. Similarly, a dual engine failure or EDP 1 failure would involve different responses and would not necessarily cause ACMP 3B to activate automatically.